01 - Preheat oven to 350°F (175°C). In a bowl, combine graham cracker crumbs, granulated sugar, and melted unsalted butter. Press the mixture evenly into the bottom and up the sides of a 9-inch pie dish.
02 - Bake the crust for 8 to 10 minutes until lightly golden. Remove from oven and allow to cool completely at room temperature.
03 - In a large mixing bowl, beat softened cream cheese until smooth. Add powdered sugar, sour cream, and vanilla extract; blend until fully incorporated and creamy.
04 - In a separate bowl, whip cold heavy cream with an electric mixer to stiff peaks. Gently fold the whipped cream into the cream cheese mixture, ensuring a smooth, airy consistency.
05 - Evenly divide the filling into three portions. Leave one portion plain for white, tint another with red gel food coloring, and tint the third with blue gel food coloring. Mix each thoroughly until colors are vibrant and uniform.
06 - Drop spoonfuls of each tinted filling onto the cooled crust in a random pattern. Using a skewer or knife, gently swirl the colors together to produce a marbled effect, without overmixing.
07 - Smooth the surface of the filling with a spatula. Refrigerate for at least 2 hours or until the filling is set.
08 - Before serving, top the pie with whipped cream and arrange fresh strawberries and blueberries as desired for presentation.